Many situations in industry, for example in food processing industries, chemical industries, petrochemicals industry and nuclear power industry, require interrogation of a mechanical structure, for example, vessel or conduit, for example a pipe or pipeline, to measure characteristics of gases, fluids and/or solids in contact with the mechanical structure, as well as an integrity of the mechanical structure itself. For example, the gases, fluids and/or solids potentially cause pressure build-up within the mechanical structures, blockages and even corrosion and/or embrittlement of the structure.
In a United Kingdom patent document GB2 399 412A (“Multiple phase fraction meter having compliant mandrel deployed within fluid conduit”, Applicant—Weatherford/Lamb Inc.), there is described a hollow mandrel which is deployable within a production pipeline at least partly within a length of a speed of sound or phase fraction meter. Sensors of the meter comprise Bragg gratings and wraps of fibre optic cable whose lengths are sensitive to acoustic pressure disturbances in the pipeline. A passive fibre optic based flow velocity meter is thereby provided, and the mandrel is optionally shaped to form an annular venture meter to provide an alternative implementation for calculating the fluid mixture density for purposes of double checking or calibration.
In a published US patent document U.S. Pat. No. 6,047,602 (“Ultrasonic buffer/waveguide”, Applicant—Panametrics Inc.), there is described a waveguide for coupling ultrasonic energy from a source on one side of a fluid-bounding wall, such as a conduit, into fluid on the other side of the wall. The waveguide has a buffer that couples to the source, and a seat with an exit face, and an intermediate portion includes a redirecting surface for internally redirecting energy propagated along the buffer towards the exit face to exit as a narrow directed beam. The waveguide core has a rectangular cross-section which is narrow, namely has an aspect ratio above two, and the buffer has a length which is effective to isolate thermally and to protect the source from the conduit. The waveguide is attached via clamp-on or welding to a pipe or spool-face. Optionally, the buffer is a thin tube which couples shear waves into the seat portion, which has a rectangular cross-section.
In a published United States patent document U.S. Pat. No. 7,185,547B2 (“Extreme temperature clamp-on flow meter transducer”, applicant—Siemens Energy and Automation Inc.), there is described a device for measuring flow in a pipe. The device includes a first metal plate mounted to the pipe. The first metal plate includes a first contact portion for contacting a wall of the pipe and a first away portion spaced apart from the wall of the pipe. The device further includes a second plate including a second contact portion spaced apart from the wall of the pipe. A first transducer is mounted to the first away portion. Moreover, a second transducer is mounted to the second away portion. The first and second transducers are thereby mounted spatially remotely from the wall of the pipe. The device provides an operational benefit that the first and second transducers are acoustically coupled via associated curved strips disposed between the contact portions and the away portions, thereby providing the transducers with a degree of isolation from the pipe. Such benefit assists when the pipe includes a flow of fluid therein a high temperatures.
In a published US patent document U.S. Pat. No. 8,090,131 B2 (“Steerable acoustic waveguide”, Applicant—Elster NV/SA), there is described a steerable acoustic waveguide apparatus which includes a plurality of plates arranged in one or more linear arrays. Steering of an acoustic beam radiated from the waveguide apparatus may be achieved through differential delays of acoustic signals resulting from differences in timing, frequency, or mode or resulting from difference in physical attributes of the plates. The waveguide apparatus serves as a thermal buffer, and may simplify access to an acoustic path in a device such as an ultrasonic flow meter.
Referring to FIG. 9, an off-shore environment is indicated generally by 10, wherein a sea-bed assembly 20 is submerged in water 15, and is coupled via one or more sea-bed pipelines 25 to a petrochemicals processing facility 30. The assembly 20 is alternatively, or additionally, coupled via the one or more pipelines 25 to a floating oil platform (not shown). The sea-bed assembly 20 is coupled via a bore hole 35, for example defined by a liner tube, to a subterranean anticline including oil and/or gas resources. In many situations, the sea-bed assembly 20 is more than 1 km deep in the water 15 and is potentially subject to pressure of 150 Bar or more. An environment experienced by the sea-bed assembly 20 is challenging for any type of sea-bed assembly 20 and associated one or more pipelines 25. Blockages, corrosion, scale deposits, leaks and similar occurring within or along the one or more pipelines 25 can potentially compromise operation of the sea-bed assembly 20 and the associated one or more pipelines 25, for example in a event of a leak or unexpected pressure surge from the anticline. Known types of sensor apparatus are not able to provide suitable measurement flexibility and yet be able to withstand, over a long period of use, harsh environmental conditions associated with operation of the sea-bed assembly 20.
In a published international PCT patent document WO2014/098613A1 (“Sensor System for Corrosion Monitoring”, Applicant—TeCom AS), there is described a sensor system for monitoring corrosion in a wall of a pipeline or vessel. The sensor system includes at least one acoustic emitter. Moreover, the sensor system includes an optical fibre provided with an arrangement for converting an acoustic signal to a corresponding optical signal. During operation, the at least one acoustic emitter emits a beam of acoustic radiation which is then reflected as a corresponding reflected beam which is received by the optical fibre to provide information for the optical signal. A sensitive material of the optical fibre allows for corrosion-related chemical parameters to be measured in a continuous fashion over a length of the optical fibre. The chemical parameters relate to at least one of: liquid water, humidity, salinity, pH and electrical conductivity. The arrangement for converting the acoustic signal to the corresponding optical signal is based upon the use of Bragg filter gratings.